A serious problem associated with zinc electrodes used in rechargeable batteries is the tendency of the active material of the electrode, viz., the zinc, to migrate from the periphery of the electrode to the center. This redistribution of the zinc, which is often termed "shape change", not only renders the edges of the zinc electrodes inactive (so-called "edge corrosion") but also reduces activity at the center of the electrode by causing densification of the zinc at the center.
A good discussion of the problem of "shape change" and various techniques for combatting this problem is found in U.S. Pat. No. 3,493,434 (Goodkin). A further patent which deals with this problem in U.S. Pat. No. 3,669,746 (Devitt et al).
The Goodkin patent is of particular interest because of the concern therein with transporting the zinc from the outer edge of the electrode to the center thereof so that, in accordance with a first embodiment, the zinc is deposited in a concave depression in the center which is specifically designed to receive replated zinc. In a second embodiment, the concentration or density of the zinc is increased in a region near the periphery of the electrode and is reduced towards the center, so as to lessen the effect of the zinc which migrates from the edge to the center and reduce densification at the center.